Earlier this week the lower house of the Russian parliament approved President Vladimir Putin’s decree on suspending the U.S.-Russian Plutonium Management and Disposition Agreement (PMDA), which requires each nation to dispose of thirty-four metric tons of plutonium from its dismantled nuclear weapons and military stockpiles. Russia has claimed that the United States is violating the agreement by changing its disposition method from irradiating the plutonium as mixed-oxide (MOX) fuel for commercial nuclear reactors to a process called dilute and dispose, but a nuclear expert says that the United States has not violated the terms of the PMDA by proposing that it change its plutonium disposition approach.

Earlier this week the lower house of the Russian parliament approved President Vladimir Putin’s decree on suspending the U.S.-Russian Plutonium Management and Disposition Agreement (PMDA), which requires each nation to dispose of thirty-four metric tons of plutonium from its dismantled nuclear weapons and military stockpiles. Edwin Lyman, a senior scientist at the Union of Concerned Scientists (UCS), answers questions about the agreement and the ramifications of the Russians’ recent action.

Q: What is your take on Russia’s suspension of the Plutonium Management and Disposition Agreement? A: It is very unfortunate that Russia has decided to suspend the PMDA. The PMDA is a very important measure that would provide assurances to the international community that the United States and Russia are disposing of plutonium stockpiles that neither country needs any more for nuclear weapons. In addition, the PMDA helps reduce the possibility that terrorist groups could steal separated plutonium. This is a very real concern in both countries. Moving forward with the agreement is in the interest of both parties.

Q: Russia has claimed that the United States is violating the agreement by changing its disposition method from irradiating the plutonium as mixed-oxide (MOX) fuel for commercial nuclear reactors to a process called dilute and dispose. Isn’t Russia therefore justified in suspending the agreement?A: The United States has not violated the terms of the PMDA by proposing that it change its plutonium disposition approach from irradiation of MOX fuel in light-water reactors to dilution and geologic disposal. The PMDA allows either party to change its approach provided that both sides agree in writing — and that has happened before. In 2010, the United States allowed Russia to change the disposition method it had committed to when the agreement was originally signed in 2000. The United States and Russia had begun discussions on the proposed new U.S. method, but formal negotiations have not taken place. Meanwhile, work on the U.S.MOX fuel fabrication plant is continuing until the viability of the alternative approach can be fully demonstrated.

UCS has concluded that the dilute-and-dispose method would render U.S. plutonium sufficiently inaccessible to satisfy the intent of the PMDA. Also, the method could be implemented much more quickly than the MOX approach. Plutonium would be diluted to a low concentration with materials that would make it difficult — although not impossible — to chemically extract the plutonium. This mixture would be placed in small quantities — about 300 grams, or 0.66 pounds, of plutonium — in large waste drums. The drums would be placed nearly half a mile underground in the Waste Isolation Pilot Plant (WIPP), a U.S. government geologic repository for nuclear waste. Over time, the salt caves where the waste is buried would collapse over the waste, rendering it irretrievable. In any case, the PMDA allows for the possibility of international monitoring. Any attempt by the United States to recover the plutonium would take a significant amount of time and would be easily observable by inspectors.

Russia has raised the concern that unlike reactor irradiation, the dilute-and-dispose method does not change the isotopic composition of plutonium from weapons-grade to reactor-grade. This is not a significant issue because the United States — and presumably Russia — can use reactor-grade plutonium to make nuclear weapons. However, to alleviate Russian concerns, the United States could obtain reactor-grade plutonium from another country, such as Japan, and blend it with U.S. weapons-grade plutonium before disposing of the mixture at the WIPP site.

Q: How will Russia’s decision to suspend the PMDA affect its relations with the United States?Russia’s decision will have less of an impact than the other disputes that are causing friction between the United States and Russia. The half-life of plutonium-239 is more than 24,000 years, which should allow sufficient time for relations between the United States and Russia to improve. Both countries likely will proceed with plutonium disposition, anyway. The difference will be that there will be no verification regime. Regardless, the United States, as a good-will gesture, should invite both Russia and the International Atomic Energy Agency to observe its plutonium disposition activities. The United States can and should provide sufficient information to convince Russian experts that dilute-and-dispose is an acceptable approach.